

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <stb_image.h>

#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

#include "shader.hpp"
#include "camera.hpp"

#include <iostream>

void framebuffer_size_callback(GLFWwindow *window, int width, int height);
void mouse_callback(GLFWwindow *window, double xpos, double ypos);
void scroll_callback(GLFWwindow *window, double xoffset, double yoffset);
void processInput(GLFWwindow *window);
unsigned int loadTexture(const char *path);

// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

// camera
Camera camera(glm::vec3(0.0f, 0.0f, 3.0f));
float lastX = SCR_WIDTH / 2.0f;
float lastY = SCR_HEIGHT / 2.0f;
bool firstMouse = true;

// timing
float deltaTime = 0.0f;
float lastFrame = 0.0f;

// lighting
glm::vec3 lightPos(1.2f, 1.0f, 2.0f);

int main()
{
  // glfw: initialize and configure
  // ------------------------------
  glfwInit();
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

#ifdef __APPLE__
  glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // uncomment this statement to fix compilation on OS X
#endif

  // glfw window creation
  // --------------------
  GLFWwindow *window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
  if (window == NULL)
  {
    std::cout << "Failed to create GLFW window" << std::endl;
    glfwTerminate();
    return -1;
  }
  glfwMakeContextCurrent(window);
  glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
  glfwSetCursorPosCallback(window, mouse_callback);
  glfwSetScrollCallback(window, scroll_callback);

  // tell GLFW to capture our mouse
  glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);

  // glad: load all OpenGL function pointers
  // ---------------------------------------
  if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
  {
    std::cout << "Failed to initialize GLAD" << std::endl;
    return -1;
  }

  // configure global opengl state
  // -----------------------------
  glEnable(GL_DEPTH_TEST);

  // build and compile our shader zprogram
  // ------------------------------------
  Shader lightingShader("/home/shihua/projects/learn_opengl/lightmapping2/glsl/cubevertexshader.glsl",
                        "/home/shihua/projects/learn_opengl/lightmapping2/glsl/cubefragmentshader.glsl");
  Shader lampShader("/home/shihua/projects/learn_opengl/lightmapping2/glsl/lampvertexshader.glsl",
                    "/home/shihua/projects/learn_opengl/lightmapping2/glsl/lampfragmentshader.glsl");

  // set up vertex data (and buffer(s)) and configure vertex attributes
  // ------------------------------------------------------------------
  float vertices[] = {
      // positions          // normals           // texture coords
      -0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f,
      0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 1.0f, 0.0f,
      0.5f, 0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 1.0f, 1.0f,
      0.5f, 0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 1.0f, 1.0f,
      -0.5f, 0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 0.0f, 1.0f,
      -0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f, 0.0f, 0.0f,

      -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f,
      0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f,
      0.5f, 0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f,
      0.5f, 0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f,
      -0.5f, 0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f,
      -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f,

      -0.5f, 0.5f, 0.5f, -1.0f, 0.0f, 0.0f, 1.0f, 0.0f,
      -0.5f, 0.5f, -0.5f, -1.0f, 0.0f, 0.0f, 1.0f, 1.0f,
      -0.5f, -0.5f, -0.5f, -1.0f, 0.0f, 0.0f, 0.0f, 1.0f,
      -0.5f, -0.5f, -0.5f, -1.0f, 0.0f, 0.0f, 0.0f, 1.0f,
      -0.5f, -0.5f, 0.5f, -1.0f, 0.0f, 0.0f, 0.0f, 0.0f,
      -0.5f, 0.5f, 0.5f, -1.0f, 0.0f, 0.0f, 1.0f, 0.0f,

      0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f,
      0.5f, 0.5f, -0.5f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f,
      0.5f, -0.5f, -0.5f, 1.0f, 0.0f, 0.0f, 0.0f, 1.0f,
      0.5f, -0.5f, -0.5f, 1.0f, 0.0f, 0.0f, 0.0f, 1.0f,
      0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f,
      0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f,

      -0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f, 0.0f, 1.0f,
      0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f, 1.0f, 1.0f,
      0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f, 1.0f, 0.0f,
      0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f, 1.0f, 0.0f,
      -0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f, 0.0f, 0.0f,
      -0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f, 0.0f, 1.0f,

      -0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f,
      0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f,
      0.5f, 0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f,
      0.5f, 0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f,
      -0.5f, 0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f,
      -0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f};
  // first, configure the cube's VAO (and VBO)
  unsigned int VBO, cubeVAO;
  glGenVertexArrays(1, &cubeVAO);
  glGenBuffers(1, &VBO);

  glBindBuffer(GL_ARRAY_BUFFER, VBO);
  glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

  glBindVertexArray(cubeVAO);
  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void *)0);
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void *)(3 * sizeof(float)));
  glEnableVertexAttribArray(1);
  glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void *)(6 * sizeof(float)));
  glEnableVertexAttribArray(2);

  // second, configure the light's VAO (VBO stays the same; the vertices are the same for the light object which is also a 3D cube)
  unsigned int lightVAO;
  glGenVertexArrays(1, &lightVAO);
  glBindVertexArray(lightVAO);

  glBindBuffer(GL_ARRAY_BUFFER, VBO);
  // note that we update the lamp's position attribute's stride to reflect the updated buffer data
  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void *)0);
  glEnableVertexAttribArray(0);

  // load textures (we now use a utility function to keep the code more organized)
  // -----------------------------------------------------------------------------
  unsigned int diffuseMap = loadTexture("/home/shihua/projects/learn_opengl/lightmapping2/image/container2.png");

  // shader configuration
  // --------------------
  lightingShader.use();
  lightingShader.setInt("material.diffuse", 0);

  // render loop
  // -----------
  while (!glfwWindowShouldClose(window))
  {
    // per-frame time logic
    // --------------------
    float currentFrame = glfwGetTime();
    deltaTime = currentFrame - lastFrame;
    lastFrame = currentFrame;

    // input
    // -----
    processInput(window);

    // render
    // ------
    glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    // be sure to activate shader when setting uniforms/drawing objects
    lightingShader.use();
    lightingShader.setVec3("light.position", lightPos);
    lightingShader.setVec3("viewPos", camera.Position);

    // light properties
    lightingShader.setVec3("light.ambient", 0.2f, 0.2f, 0.2f);
    lightingShader.setVec3("light.diffuse", 0.5f, 0.5f, 0.5f);
    lightingShader.setVec3("light.specular", 1.0f, 1.0f, 1.0f);

    // material properties
    lightingShader.setVec3("material.specular", 0.5f, 0.5f, 0.5f);
    lightingShader.setFloat("material.shininess", 64.0f);

    // view/projection transformations
    glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);
    glm::mat4 view = camera.GetViewMatrix();
    lightingShader.setMat4("projection", projection);
    lightingShader.setMat4("view", view);

    // world transformation
    glm::mat4 model = glm::mat4(1.0f);
    lightingShader.setMat4("model", model);

    // bind diffuse map
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, diffuseMap);

    // render the cube
    glBindVertexArray(cubeVAO);
    glDrawArrays(GL_TRIANGLES, 0, 36);

    // also draw the lamp object
    lampShader.use();
    lampShader.setMat4("projection", projection);
    lampShader.setMat4("view", view);
    model = glm::mat4(1.0f);
    model = glm::translate(model, lightPos);
    model = glm::scale(model, glm::vec3(0.2f)); // a smaller cube
    lampShader.setMat4("model", model);

    glBindVertexArray(lightVAO);
    glDrawArrays(GL_TRIANGLES, 0, 36);

    // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
    // -------------------------------------------------------------------------------
    glfwSwapBuffers(window);
    glfwPollEvents();
  }

  // optional: de-allocate all resources once they've outlived their purpose:
  // ------------------------------------------------------------------------
  glDeleteVertexArrays(1, &cubeVAO);
  glDeleteVertexArrays(1, &lightVAO);
  glDeleteBuffers(1, &VBO);

  // glfw: terminate, clearing all previously allocated GLFW resources.
  // ------------------------------------------------------------------
  glfwTerminate();
  return 0;
}

// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow *window)
{
  if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
    glfwSetWindowShouldClose(window, true);

  if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
    camera.ProcessKeyboard(FORWARD, deltaTime);
  if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
    camera.ProcessKeyboard(BACKWARD, deltaTime);
  if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS)
    camera.ProcessKeyboard(LEFT, deltaTime);
  if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS)
    camera.ProcessKeyboard(RIGHT, deltaTime);
}

// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow *window, int width, int height)
{
  // make sure the viewport matches the new window dimensions; note that width and
  // height will be significantly larger than specified on retina displays.
  glViewport(0, 0, width, height);
}

// glfw: whenever the mouse moves, this callback is called
// -------------------------------------------------------
void mouse_callback(GLFWwindow *window, double xpos, double ypos)
{
  if (firstMouse)
  {
    lastX = xpos;
    lastY = ypos;
    firstMouse = false;
  }

  float xoffset = xpos - lastX;
  float yoffset = lastY - ypos; // reversed since y-coordinates go from bottom to top

  lastX = xpos;
  lastY = ypos;

  camera.ProcessMouseMovement(xoffset, yoffset);
}

// glfw: whenever the mouse scroll wheel scrolls, this callback is called
// ----------------------------------------------------------------------
void scroll_callback(GLFWwindow *window, double xoffset, double yoffset)
{
  camera.ProcessMouseScroll(yoffset);
}

// utility function for loading a 2D texture from file
// ---------------------------------------------------
unsigned int loadTexture(char const *path)
{
  unsigned int textureID;
  glGenTextures(1, &textureID);

  int width, height, nrComponents;
  unsigned char *data = stbi_load(path, &width, &height, &nrComponents, 0);
  if (data)
  {
    GLenum format;
    if (nrComponents == 1)
      format = GL_RED;
    else if (nrComponents == 3)
      format = GL_RGB;
    else if (nrComponents == 4)
      format = GL_RGBA;

    glBindTexture(GL_TEXTURE_2D, textureID);
    glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
    glGenerateMipmap(GL_TEXTURE_2D);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    stbi_image_free(data);
  }
  else
  {
    std::cout << "Texture failed to load at path: " << path << std::endl;
    stbi_image_free(data);
  }

  return textureID;
}
